We tested the hypothesis that dietary nitrate (NO3−)-rich beetroot juice (BR) supplementation could partially offset deteriorations in O2 transport and utilization and exercise tolerance after blood donation. Twenty-two healthy volunteers performed moderate-intensity and ramp incremental cycle exercise tests prior to and following withdrawal of ∼450 ml of whole blood. Before donation, all subjects consumed seven 70-ml shots of NO3−-depleted BR [placebo (PL)] in the 48 h preceding the exercise tests. During the 48 h after blood donation, subjects consumed seven shots of BR (each containing 6.2 mmol of NO3−, n = 11) or PL (n = 11) before repeating the exercise tests. Hemoglobin concentration and hematocrit were reduced by ∼8–9% following blood donation (P < 0.05), with no difference between the BR and PL groups. Steady-state O2 uptake during moderate-intensity exercise was ∼4% lower after than before donation in the BR group (P < 0.05) but was unchanged in the PL group. The ramp test peak power decreased from predonation (341 ± 70 and 331 ± 68 W in PL and BR, respectively) to postdonation (324 ± 69 and 322 ± 66 W in PL and BR, respectively) in both groups (P < 0.05). However, the decrement in performance was significantly less in the BR than PL group (2.7% vs. 5.0%, P < 0.05). NO3− supplementation reduced the O2 cost of moderate-intensity exercise and attenuated the decline in ramp incremental exercise performance following blood donation. These results have implications for improving functional capacity following blood loss.
- blood withdrawal
- beetroot juice
- O2 transport
- O2 uptake
- exercise performance
- nitric oxide
- Copyright © 2016 the American Physiological Society
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